One aspect generally relates to a Cr, Ni, Mo and Co alloy, with tightly controlled levels of impurities. One aspect further relates to a process for the preparation of an alloy, an alloy obtainable therefrom, a lead, and the use of a lead in medical devices, such as pacemakers.
Much investigation in recent years has been directed to a search for new high performance alloys, such as for medical applications where a very high value is placed on reliability and materials are required which exhibit a low failure rate even over a long time period.
Cardiac Pacemakers, Implantable Cardioverter Defibrillation Devices and Cardiac Resynchronization Devices are applications where reliability is particularly important, especially in terms of resistance to physical fatigue and to chemical corrosion. Invasive surgery is required to implant a pacemaker into the body or remove or replace parts, and it is highly desirable for the individual components of the pacemaker to have a long working life in order to reduce the requirement for surgical intervention. Furthermore, it is desirable for the working life to have a low variance. In a heart pacemaker, one component which is exposed to a particularly high amount of stress during normal operation is the so called lead which connects the implantable pulse generator to the heart tissue. A flexible lead is required in order to connect the implantable pulse generator to the heart tissue without imposing undue physical stress on the heart and the lead flexes during normal operation, typically repetitively with a frequency on the order of that of a human heart beat. A high resistance to fatigue is therefore required in the lead in order to withstand frequent physical stress over a long period of time. A high resistance of the lead to corrosion is important not only in terms of the lifetime of the component, but also in terms of reducing toxicity to the body.
WO 2005026399 A1 discusses an approach to improving the properties of an alloy by reducing the content of titanium nitride and mixed metal carbonitride.
US 2005/0051243 A1 focuses on alloys with a reduced content of nitrogen.
There persists a requirement for alloys having improved performance, such as with regard to improving resistance to physical fatigue.
For these and other reasons, a need exists for the present invention.